Pump



May 20, 1947.- c. E. ANDERSON 2,420,806

` PUMP Filed Nov. 26, 1945 :s Sheets-sheet 2 INVEN TOR.

@aI/'Z n dey-Sow ATTK 1 Patented May 20,1947l UNITED STATES PATENT oFElcE Carl E. Anderson, Newark, N. J.

Application November 26, 1945, Serial No. 630,844

This invention relates to rotary hydraulic pumps and motors of the type embodying a rotatable cylinder block having a plurality of radially disposed cylinders each provided with a reciprocatory piston, which pistons operate against a surrounding thrust member.

ze claims. '(ci. ins-161) 2 Another object of the invention is to provide a pump of the radial cylinder type in which, during each rotation of the rotor, each cylinder and As is well understood in theart,` a machine of this nature may function as a pump when the cylinder block is rotated from an external source of power and the cylinders are properly connected to suitable intake and discharge conduits carrying oil or other liquid. It is also well known that a similar device will function as a rotary hydraulic motor when liquid is properly delivered under pressure into the cylinders and permitted to be discharged therefrom substantially pressure free. l

Frequently two nected together so that the first acts as a pump to deliver oil, under high pressure, into the second which, in turn, converts the hydraulic pressure into rotary motion in a power delivery shaft and then returns the spent oil either into the intaxe port of the pump for recirculation or into a reservoir with which thei intake'port of the pump is connected. The speed of rotation of the power delivery shaft is directly 'proportional .to

such units are operatively conthe rate of delivery of oil by the pump unit. To

the end that the speed of the power delivery shaft may be varied, pumps of this nature are so con' structed and arranged that, under a constant varied rf* but it is to be understood that,the invention is equally applicable to a hydraulic motor and that, therefore, the term pump, as used in this specication and in the 4appended. claims, is intended to define either a hydraulic pump or a hydraulic motor.

The term rotorl will hereinafter be used to designate the rotary element which provides the radially disposed cylinders. The term oil" is intended to mean any suitable liquid.

ri'his invention has as an object to provide an improved hydraulic pump of the radial cylinder type in which objectionable side thrusts on ,the rotor and its supporting element are eliminated or eiectively counteracted.

Another object of the invention is to provide an improved hydraulicl pump of this type in which a hydraulic balance is maintained radially by doing equal amounts of hydraulic work on opposite sides of the axis of the rotor, or in other words, 180 degrees apart.

its cooperating piston will elfect two complete pumping operations, thereby doubling the output of the pump as compared with prior constructions. y

Still another object is to provide improved means for varying the displacement effected by each piston, whereby pump delivery may be varied from zero to maximum during constant speed rotation of the rotor.

A further object of the invention is to provide improved valve means for starting or stopping the flow of oil to and from the pump or for reversing its direction of flow during continuous running of the pump. whereby' either of two ports may be used selectively as the intake port, while the other serves as a discharge port. This feature is usefulfor example, when the pump is connected in a closed circuit system with a similar rotary motor unit or with the opposite ends of a power cylinder; the forward and reverse flows causing the rotary motor to rotate in for-Y ward and reverse directions and the piston of the power cylinder to bev reciprocated back and forth.

A still further object is to eliminate al1 lateral or side thrust on the pump pistons, which thrust, in prior` constructions,` has produced friction which resulted in undue wear in the cylinder walls and pistons. This has been accomplished by so constructing and arranging the cylinders,

the` pistons and the means for transmitting the thrust of the surrounding thrust member to the pistons, that such thrusts are transmitted to the pistons within the cross-sectional area of the pstons and in a straight line parallel to their axes.

With the above and other objects in view, as will hereinafter appear, the invention comprises the devices, combinations and arrangements of. parts hereinafter set forth and illustrated in the accompanying drawings of a preferred embodiment of the invention, from which the several features of the invention and the advantages attained thereby will be readily understood by those skilled in the art.

In the drawings: t

Fig. 1 is a side elevation of a pump or motor embodying the present invention.

Fig. 2 is a longitudinal horizontal section substantially on the line/2 2 of Fig. 4, showing the thrust member in its neutral position.`

Fig. 3 is a longitudinal vertical .section sub. stantially on the line 3-3 of Fig. 4 showing the thrust member in its maximum operating posi tion.

Fig. 4 is a transverse section on the line 4-4 of Fig. 3 with the control valve turned forty-five degrees.

Fig. 5 is a longitudinal sectional view of the control valve and the casing thereon which provides the inlet and outlet ports for the pump, showing the valve in the same position in the casing as in Fig. 3 and in which it effects what may be called a forward flow from the pump.

Fig. 6' is a sectional view on the line 8-8 of Fig. 5.

Fig. '7 is a sectional view on the line 1-1 of Fig. 5.

Fig. 8 is a view similar to Fig. 5 but showing the control valve turned in the casing ninety degrees from the position shown in Fig. 5, to effect a reverse flow from the Pump- Fig. 9 is a section on the line 9-9 of Fig. 8.

Fig. 10 is a section taken on the line III- I0 of Fig. 8.

Fig. 11 is a view similar to Fig. 9, but with the control valve turned forty-five degrees relative to the valve casing to an intermediate or neutral position in which there is no flow of fluid either to or from the pump.

Fig. 12.is a schematic sectional view through the control valve and pump cylinders. with the valve in the same position as shown in F18. 11.

Fig. 13 is a face view of a portion of the rim of the rotor. f

Fig. 14 is a detail cross section through the rotor on the line I4-ll4 of Fig. 13.

Fig. 15 is a central longitudinal section through one of the multi-part pistons.

Fig. 16 is a sectional view taken on the line Iii-I6 of Fig. 1.5.

Referring more specifically to the drawings. the invention is disclosed as embodied in a variable displacement pump having a main` casing' C comprising a cylindrical central body member I having supporting feet 2, a cup-like end cover 3 closing one lend of the body member and an end plate 4 closing the other end of the body member and serving as a support for the working elements of the machine. The end plate 4 is formed with an inwardly projecting hub E in which is journaled a portion of a cylindrical valve member 6. This valve member is normally held stationary but is capable of being turned manually through steps of ninety degrees each for the purpose of reversing the direction of the flow through the pump, as hereinafter will be described.

A power shaft 1 is journaled within an axial bore 6x in the valve member 8 and may be driven from any suitable source outside the pump, such for example, as an electric motor (not shown) connected to the splined outer end 8 thereof. At its inner end the shaft 1 has a reduced portion 9 upon which is secured, by a nut I0, a rotor R, in the nature of a cylinder block II, provided with a plurality of radially disposed pump cylinders I2, of which fourteenare shown, but any other suitable number may be employed. The rotor I I is Journaled, with a close running t, on the inner cylindrical end portion 6* of the valve member 6. Each cylinder I2 has fitted therein the cylindrical portion I3 of a piston p which during operation of the pump is urged outwardly by centrifugal force. r

Surrounding the rotor II and the pistons p, is a thrust member T, herein shown as a cup-like element -I4 having a cylindrical bore I5, the wall of which affords a thrust surface adapted'to engage the outer ends of the pistons p as herein- 4 after will be described. To reduce friction between the thrust member and the pistons p the member is preferably mounted so as to be rotatable with the rotor Rr The thrust member` T is shown as formed with a rearwardly projecting'stub shaft I8 which is rotatably journaled in the hub portion I1 of a yoke I8 and held therein by a nut I3 and washer 2l. The arms I8s and I8h of the yoke I8 are journaled, respectively, on a stud 2l, secured in the casing member I, and on a stub shaft 22 journaled in the casing member I and diametrically opposite the stud-2|. The axes of the stud 2l and the shaft 22 are located in the plane of the axes of the cylinders I2 and the pistons p and intersect the axis of the power shaft 1. 'A hand lever 23 fixed to the outer end of the shaft 22 serves as means for turning the yoke I8 and the thrust member T carried thereby about the axes of the stud 2| and shaft 22, for a purpose hereinafter to be described. Any suitable or preferred means, such for example, as a bolt 24, carried by the depending arm 23'* of the hand lever 23 and having its head tracking an arcuate T-slot 24* in the casing member I, and a clamp nut 2l, threaded onto the bolt 24, is provided for locking the yoke I8 and the thrust member T in their various positions of angular adjustment.

Secured to the outer face of the end plate 4, opposite the hub 5, is a valve casing 26, provided with two ports 21 and 28 one of which serves as an inlet for substantially pressure free oil while the other serves as an outlet port for the high pressure oil ejected by the pump pistons. The flmctions of these ports may be reversed, as hereinafter will be described. Suitable conduits, c and c', are connected to the ports 21 and 28 to conduct oil to and away from the valve casing.

The cylindrical control valve 6 is journaled in the hub 5 and carries the valve casing 28 and' is held against endwise movement therein in one direction by an annular shoulder 29 on the valve abutting the innerend of the hub 5 and in the opposite direction by a retaining ring 3l! fitted into an annular groove 3l in the outer end of the valve cylinder and abutting the outer face of the valve casing 28. Oil seals s fitted into cavities d in the valve casing 28 effect an oil tight joint between the valve and the casing. 'I'he valve 8 is formed with two longitudinal bores or ports 32 which, at one end, connect with arcuate chambers 32'A formed in the valve cylinder within the rotor R and similar bores or ports 33 which also connect with arcuate chambers 33* in the inner end of the valve cylinder and spaced ninety degrees from the chambers 32, In the setting of the valve in the position shown in Figs. 4, 5, 6 and '1 the outer ends of the bores 32 are connected with a chamber 34 in the valve casing 28 and that chamber in turn is connected with the port 28 which then serves as an inlet port. Thus oil flows through the conduit c', port 28, chamber 34, and bores 32 into the chambers 32n which Supply the oil to the inner ends of the adjacent cylinders I2 as the pistons I3 are noved outwardly by centrifugal force. In this same setting of the valve the arcuate chambers 33n receive oil from the adjacent cylinders I2 due to the inward movement of the pistons therein. Oil from the chambers 33, which then are high pressure chambers, flows through the bores 33 and into a chamber 35 in the valve casing,A and from there outwardly through the port 21 andconduit c.

into the arcuate chambers 32'L and thence through bores 32, chamber 34, port 23 and conduit c'.

During the turning of the valve ninety degrecs from the position shown in Figs. 4, 5, 6 and` '1 to the position shown in Figs. 8, 9 and 10, the

l slidingly nts a projecting end portlon`l4 of each pin 54. The engagement of the pin with the walls of the groove I3 prevents the outer portion Il, 5I, 52 of the piston p from rotating in the counterbore il while permitting it freely axially of the counterbore.

From the foregoing, it will be understood that to move the walls of the counterbores 55 afford bearing flow of oil is gradually reduced and finally ceases completely at forty-five degrees. 'I'his is due to the fact thatl all of the bores 32 and 33 are then cut of! from the chambers 34 and 35 and the outward movement of one-half of the number of ,pistons I3 in the cylinders I2 takes the oil which is discharged from the other. half of the number of cylinders by the inward movement of the pistons therein. See Figs. 1l and 12. This gradual shutting off and starting up of the now helps to eliminate sudden hydraulic shocks Ain the pipe lines when reversing. Within the valve casing 26 the valve 6 is formed with arcuate periphera1 channels 32b and 33b connected, respectively, with the bores 32 and 33. I'hese channels provide inlets and outlets for the oil to and from the pump during the turning of the valve until the neutral position, shown in Figs. l1 and 12, is reached.

The means for` turning the valve E comprises a gear 35 formed on the annular shoulder 23 which abuts the inner end of the hub 5, a gear 31 secured on a stub shaft 38 journaled in a boss 39 depending from the hub 5 and meshing with the gear 35, a pair of bevel gears and 4I of whch'the former is secured to the shaft 3l and direction, gives to the valve 5 an angular movement of ninety degrees, thereby reversing the flow of the fluid through the pump. y

As shown most clearly in Figs. 2, 3, 4, 15 and 16, each piston p is formed of a plurality of parts viz. the cylindrical part I3 which is tted into the cylinder I2, a U-shaped yoke 50, the base 5I of whichis circular in cross section and bears f upon the outer end of the part I3, and a thrust roller 52 journaled, by needle bearings 53,' on a pin 54 fitted into bores in the arms 50* of the yoke 50. The thrust rollers engage and bear upon the wall of the bore I5 in the thrust member T hereinbefore mentioned. The base `5I and the outer surfaces of the arms of each piston p is slidingly fitted in a counterbore 55 formed in the periphery of the rotor R, in axial alignsurfaces for the outer portions of the pistons p which are of ample area to withstand, without undue wear, any lateral thrust which maybe applied thereto by reaction of the thrust member T on the rollers 52,` and to transmit such thrusts to the outer ends of the cylindrical portions`|2 of the pistons within their cross sectional areas and in a straight line parallel to their axes. 'I'his construction eliminates al1 side thrusts on the portions-I3 `of the pistons and thereby reduces wear in the cylinders I2 and on the portions I3.

Operation y with the handle z3 in thefpesiticn sifown in full lines in Fig. 1, and consequently with the yoke, Il and the thrust member T in the neutral position shown -in Fig. 2; with the vshaft 1 rotated from anysuitable-souree of-'powem and with the valve 3 set in a position to admit oil into .the cylinders I2; the rotor R and all the parts carried thereby will be rotated on the valve 6. Centrifugal force tends to move the pistons p outwardly and forces the rollers 52 into pressure contact with the thrust surface of the bore I5 in the thrust member T. Outward pressure on ment with one of the cylinders I2 (Figs. 13 and Also formed in the periphery of the rotor, and connecting the counterbores 55, is an annular groove 55, U-shaped in cross section, into which the pistons androtation of the rollers with the rotor R set up forces which causes the thrust horiaontal'axes of the stud 2| and shaft 22 to the position shown in Fig. 3. Centrifugal force continues to urge the pistons' p outwardly and maintains the rollers 52 in pressure contact with the bore I5 of the thrust member T. Pressure of the pistons on the thrust member causes the thrust member to continue to rotate with and at the same speedas the rotor. The rotor and thrust member are now rotated about axes which are at an acute angle to each other and due to that angularity the cylindrical bore I5 of the thrust member presents an elliptical thrust path to the rollers 52 of the pistons p with the major axis of the ellipse extending vertically, as shown in Figs. 3 and 4. As will best be understood from Fig. 4, each ninety degrees of rotation of the lrotor and the thrust member causes those rollers 52, which were on the major axis of the elliptical thrust path of 'the thrust member, to be moved to the minor axis of. the elliptical thrust path while those on the minor axis will be caused to move to the major axis. Thus during each degrees of rotation each piston is given a complete working cycle, i. e. an intake stroke and a discharge stroke, whereby each complete rotation produces two complete pumping operations in each cylinder.'

In addition toits rotation with the thrust member T each piston roller 52 is caused to travel along the innerperlphery of the thrust member 7 inapathwhichispracticallyparelleltotheaxis oi'thethrustmember. Thiswlllbestbeunderstood from an inspection o! Fig. 3. in which the upper roller' i2 is shown near the bese of the thrust member while the lower roller is shown near the outer edge thereof.

As hereinbefore stated the yoke Il and thrust member .T may be set in various positions between the extremes shown in Figs. 2 and 3. In each such setting, the maior axis of the elliptical thrust path of the rollers 52 in the thrust member T will Ybe diiferent and therefore strokes of different length will 'be transmitted Ato the pistons p, thus varying pump displacement;

When the control valve is in the neutral poeltion shown in Fig. li there is no pressure exerted on the pistons p or on the thrust member T and the thrust member may, therefore; then be easily shifted from one position to another.

From the foregoing it willbe perceived vthat this invention has provided an improved variable displacement pump and motor oi the radial cylinder type in which a plurality of pumping operations are ellected by each piston during each rotation of therotor; in which radial thrusts on the rotor and its supporting element are effectively counteracted; in which a hydraulic balance is maintained radially by doing equal amounts'of hydraulic work on opposite sides of the axis of the rotor; and in which pump delivthe position of said uipticllthllllt plth said pistons.

and normally urged outwardly therein;

ery readily may be varied, brought to zero or reversed without producing 'hydraulic shocks in the pump or in the system to which the pump is connected. o

Having thus set forth the nature of the invention. what I claim herein is:

1. A variable ldisplacement hydraulic pump comprising a rotor provided with a plurality of radially disposed cylinders; means to rotate said rotor; a reciprocatory piston in each of said cylinders; a thrust member having a cylindrical bore aifording an elliptical thrust path surrounding said rotor and acting on said pistons to give to each piston a plurality of working cycles during a single rotationlof said rotor; and means to ad- Just said thrust member to vary the strokes of said pistons.

2. A variable displacement hydraulic pump comprising a rotor provided with a plurality of radially disposed cylinders; means to rotate said rotor; a reclprocatory piston in each of said cylinders, each of said pistons ,comprising a cylindrical portion in the cylinder and an enlarged outer end portion; a thrust member having a cylindrical bore surrounding said rotor and affording an elliptical thrust path engaging the outer ends of said pistons for transmitting thrusts to said cylindrical portions withinl the cross sectional area thereof and in a direction parallel to their axes, to give to each of said pistons a plurality oi working cycles iree of side thrusts during a single rotation of said rotor; and means to adjust the position of said thrust member to vary said elliptical path and thereby vary the strokes of said pistons.

3. A variable displacement hydraulic pump comprising a rotor provided with a plurality o! radially disposed cylinders; means to rotate said rotor; a reciprocatory piston in each of said cylinders; a thrust member surrounding said rotor and presenting to the outer ends of said pistons an elliptical thrust path whereby. during rotation of said rotor. said thrust path gives to each piston a plurality of working cycles during a sinrle rotation of said rotor; and means to adjust 4. A hydraulic pump comprising a rotor provided with a plurality ot radially disposed cylinders; means to rotate said rotors; a reciprocatory piston located in each of said cylincers an a thrust member having a cylindrical bore surrounding laid rotor and acting on the outer ends o! said pistons, said bore being arranged with its axis at an acute angle to the axis of rotation of said'rotor whereby the wall of said bore presents to said pistons an elliptical path of contact.

5. A hydraulic pump comprising a rotor provided with-a plurality o! radially disposed cylinders; means to rotate said rotor; a reciprocatory piston in each of said cylinders; a thrust member having a cylindrical bore surrounding said rotor and engaging the outer ends of said pistons; andmeans to hold said thrust member in a position in which the axis of said bore forms an acute angle with the axis oi rotation of said rotor whereby the wall of said bore presents an elliptical thrust path to said pistons.

6. A variable displacement hydraulic pump comprising a rotor provided with a plurality oi radially disposed cylinders; means to rotate said rotor; a reciprocatory piston in each of said cylinders; a thrust member having a cylindrical bore surrounding said rotor and engaging the outer ends of said pistons; means to support said thrust member with its bore coaxial with said rotor to eiiect zero pump displacement; and means to shift said thrust member to a position in which the axis of said Ibore forms an acute angle with the axis of rotation of said rotor and in which the wall of said bore presents an elliptical thrust path to said pistons whereby said pistons are reciprocated in said cylinders to render the pump eiective.

7. A variable displacement pump as set forth in claim 6 in which means is provided for shifting said thrust member angularly to a plurality of operative positions in each of which a cliiler ent elliptical thrust path is presented to said pistons thereby to vary pump displacement, and means for holding said thrust member in its various positions of adjustment.

8. Ay variable displacement hydraulic pump comprising a. casing; a rotor journaled in said casing and provided with a plurality of radially disposed cylinders; means to rotate said rotor; a reciprocatory piston in each of said cylinders; a yoke journaled within said casing on an axis transverse to the axis of rotation of said rotor;

a thrust member supported in said yoke and having a cylindrical bore surrounding said rotor and engaging the outer ends of said pistons; means to shift said yoke to move said thrust member from a position in which said bore is coaxial with said rotor to a position in which the axis of the bore is transverse to the axis of rotation oi the rotor V and in which the wall of said bore presents an elliptical thrust path to said pistons; and means to secure said yoke in its adjusted position.

9. A variable displacement pump comprising a casin'g; a rotor iournaled in said casing and provided with a plurality of radially disposed cylinders; means to rotate said rotor; a reciprocatory piston located in each of said cylinders and normally urged outwardly therein during operation of the pump; a yoke journaled within said casing on an axis transverse to the axis of rotation of said rotor; a thrust member journaled in said yoke onan axis in alignment with the axis of rotation of the rotor and having a cylindrical bore surrounding said rotor and frictionally engaging the outer ends ofsaid pistons whereby rotation of said pistons with said rotor causes similar rotation of said thrust member; and means to shift said yoke to a position in which the axis of said thrust member forms an acute angle to the axis of rotation of said rotor and in which the wall of said bore presents to said pistons 'an elliptical path of contact.

10. A variable displacement hydraulic pump comprising a casing; a valve member mounted in said casing and provided with a plurality of supply ports and a plurality of discharge ports; a rotor journaled coaxially with said valve member and provided with a plurality of radially disposed cylinders adapted to be connected successively with said supply and discharge ports; means to rotate said rotor; a reciprocatory piston in each of said cylinders; a rotatable thrust member surrounding said rotor and rotatable therewith, said thrust member having a cylindrical bore the axis of which is arranged at an 4acute angle to and intersects the axis of rotation of said rotor, the wall of said bore being in engagement with the outer ends of said pistons and transmitting thereto a plurality of working cycles during each rotation of the rotor; and means to adjust the angular position of said thrust member relative to the axis of said rotor to vary the strokes of said pistons.

ll. A hydraulic pump comprising a casing; a cylindrical valve member mounted in said casing and provided with a plurality of longitudinal supply ports and a plurality of longitudinal discharge ports; a rotor journaled on said valve member and provided with a plurality oi' radially disposed cylinders adapted to be connected successively with said `supply and discharge ports; means extending through said valve and connected to the rotor to rotate the rotor; `a reciproca,- tory piston in each of said cylinders and a thrust member having a cylindrical bore affording an elliptical thrust path surrounding said ,rotor and acting on the outer ends of said pistons to give to each piston a plurality of working cycles dur.. ing each rotation of said rotor.

l2. A variable displacement hydraulic pump comprising a main casing; a valve casing secured to the main casing and having inlet and outlet ports; a cylindrical valve member mounted in said casings and provided with a plurality of longitudinal supply ports connected with one oi the ports in the valve casing and a plurality of longitudinal discharge ports connected to the other port in the valve casing, a rotor journaled coaxially with said valve member and provided with a plurality of radially disposed cylinders adapted to be connected successively with said supply and discharge ports; means to rotate said rotor; a reciprocatory piston in each of said cylinders; a thrust member surrounding said rotor and affording an elliptical'thrust path acting on said pistons to give to each piston a plurality of work-v ing cycles during each rotation of said rotor; and

means to vary the length of the major axis of said v ply ports and a plurality of discharge portsjl a y rotor journaled coaxially with said valve member and provided with a plurality of radially disposed cylinders adapted to be connected successively with said supply` and discharge ports: means to rotate said rotor; a reciprocatorypiston in each oi' said cylinders; an angularly adJustable thrust member having a cylindrical bore surrounding said rotor and affording an elliptical thrust Path acting on said pistons to give to each piston a plurality of working cycles during each rotation of said rotor: and means to change the angular position of said thrust member to vary the length of the major axis of said elliptical thrust path, thereby to vary the strokes or said pistons and the consequent pump displacement.

14. A hydraulic pump comprising a casing, a cylindrical valve member journaled in said casing and provided with a plurality of supply ports and a plurality of discharge ports; a rotor journaled on said valve member and provided with a plurality of radially disposed cylinders adapted, during the rotation of the rotor, to be connected successively with said supply and discharge ports; means to rotate said rotor; a reciprocatory piston in each of said cylinders; a thrust member having a cylindrical bore surrounding said rotor and affording an elliptical thrust path engaging the outer ends of said pistons to give to each piston a plurality of working cycles during each ber; a cylindrical valve member journaled in said casings and provided with a pair of longitudinal supplyports and a pair of longitudinal discharge ports each port being connected with one of said chambers; a rotor journaled kcoaxially with said valve member and provided with a plurality of radially disposed cylinders adapted, during the rotation of the rotor, to be connected successively with said supply and discharge POIts; means to rotate said rotor; a reciprocatory piston in each of said cylinders; a thrust member having a cylindrical bore surrounding said rotor with the inner wall thereof engaging the outer ends of said pistons; means to shift said thrust member to cause said bore to present to said pistons an elliptical thrust path adapted to give to each piston a plurality of working cycles during each rotation of the rotor; and means to rotate said valve member to cause each oi' said supply and discharge ports to be connected with the other of said chambers, thereby to reverse the direction of' the ilow through the pump. er

16. A hydraulic pump comprising a casing; a cylindrical valve member journaled in said casing and provided with a plurality of supply ports and a plurality of discharge ports; a gear on said 1 valve member; a rotor journaled coaxially with said valve member and provided with a plurality of radially disposed cylinders adapted, during the rotation of the rotor, to be connected successively with said supply and discharge ports; means to rotate said rotor; a reciprocatory piston in each of said cylinders; a member having a cylindrical -bore affording an elliptical thrust path surrounding said rotor and acting on said pistons to give to each piston a plurality of working cycles during each rotation of the rotor; and means to shift said valvemember to reverse the positions of the intake and discharge ports therey by to reverse the direction of the ilow through the pump; saidvalve shifting means comprising a shaft iournaled in said casing and extending through a wall thereof, a gear connection between the inner end of said shaft and said gear, and a manually actuableelement on the outer end of said shaft to rotate the shaft.

17. A hydraulic pump comprising a casing having an inwardly projecting hub; a cylindrical valve member journaled in said hub and provided with a plurality of longitudinal supply ports and a plurality of longitudinal discharge ports; a rotor journaled on said valve member and provided with'a plurality of radially disposed cylinders adapted, during the rotation of the rotor, to be connected successively with said intake and discharge ports; a rotary shaft extending through said valve and connected to the rotor to rotate the rotor; a reciprocatory piston in each of said cylinders; a member having a cylindrical bore affording an elliptical thrust path surrounding said rotor and acting on said pistons to give to each piston a plurality of working cycles during each rotation of the rotor; and means to rotate said valve member to reverse the positions of the supply and discharge ports thereby reverse the direction of the ilow through the pump.

18. A hydraulic pump comprising a casing; a rotor journaled therein and provided with a plurality of radially disposed cylinders; a reciprocatory piston in each of said cylinders; means to rotate said rotor to cause said pistons to be moved outwardly in said cylinders by centrifugal force and alternately to connect said cylinders with intake and discharge ports; a thrust member mounted in said casing and having a cylindrical bore normally coaxial with the axis of rotation of said rotor, the wall of said bore surrounding said pistons and opposing their outward movement; and means for moving said thrust member to a position in which the axis of said bore is at an acute angle to the axis of rotation of the rotor whereby said wall presents to said pistons an elliptical thrust path which, during each rotation oi the rotor, shifts each piston inwardly a plurality of times in opposition to said centrifugal force, thereby to effect a plurality of working cycles.

19. A hydraulic pump comprising a lrotor provided with a plurality of radially disposed cylinders and a plurality of cylindrical chambers located outwardly from said cylinders and in alignment therewith; a plurality of multipart reciprocatory pistons each including a cylindrical portion located in one of said cylinders and an enlarged head detached from but contacting said cylindrical portion and located in the aligned chamber; means to rotate said rotor; and means affording an elliptical thrust path surrounding said rotor and acting on the heads of said pistons to give to each piston a plurality of working cycles during each rotation of the rotor.

20. A hydraulic pump comprising a rotor provided with a plurality of radially disposed cylinders having their axes in a plane and a plurality *l of radially disposed cylindrical chambers located 'outwardly from the cylinders and in alignment therewith; means to rotate the rotor; a recipro- `-catory piston located in each of said cylinders and having a detached head in the aligned chamber; a thrust roller journaled in each of said heads; a thrust member surrounding said rotor and presenting to said thrust rollers an elliptical thrust path in the plane containing the axes of said cylinder, said thrust path giving to the rollers, and thereby to each piston, a plurality of working cycles during each rotation of the rotor.

21. A hydraulic pump comprising a rotor provided with a plurality of radially disposed cylinders and a cylindrical chamber located outwardly of each cylinder and in alignment therewith, said chambers having materially greater diameters than said cylinders; means to rotate said rotor; a reciprocatoryv piston located in each of said cylinders and each comprising an oil displacement member and an enlarged detached cylindrical head reciprocally mounted in the aligned chamber; a thrust roller journaled in each of said heads; a thrust member surrounding said rotor and presenting to said thrust rollers an elliptical thrust path, whereby said thrust path gives to each of said rollers and thereby to each of said oil displacement members a plurality of working cycles during each rotation of the rotor, said parts being so constructed and arranged that any side thrusts received by said heads from said thrust member are transmitted to the walls of said chambers and said heads transmit to said oil displacement members thrusts in a direction parallel to their axes only.

22. A hydraulic pump comprising an annular rotor provided with a plurality of radially disposed cylinders and a, cylindrical chamber located outwardly of each cylinder and in alignment therewith; an annular groove in the periphery of said rotor and connecting said chambers; means to rotate said rotor; a reciprocatory piston in each of said cylinders, each of said pistons having a bifurcated head portion in the aligned chamber; a pin journaled in the furcations of each of said heads and projecting to one side thereof and fitted into said annular groove to prevent rotation of said heads in said chambers; a. thrust roller journaled on each of said pins; and a thrust member surrounding said rotor and acting on said rollers during rotation of the rotor to reciprocate said pistons in said cylinders.

CARL E. ANDERSON.

REFERENCES `CITED The following references are of record in the file of this patent:

lUNITED STATES PATENTS Number Name Date 1,077,980 Hele-Shaw Nov. 11, 1913 1,974,961 Johnson Sept. 25, 1934 2,382,389 Benedek Aug. 14, 1945 1,436,863 Crouse Nov. 28, 1922 1,793,007 Pearson Feb. 17, 1931 2,077,389 Benedek Apr. 20, 1937 2,130,299 `Ernst Sept. 13, 1938 2,260,859 Neuland Oct. 28, 1941 2,262,593 Thomas et al Nov. 1l, 1941 2,328,717 Glasner Bept. 7, 1943 

